Publication Abstract

Development of Design Practice for Piles in Stiff Glacial TillKenneth Gavin

Design practice for piles installed in Irish glacial till has developed in an ad-hoc manner, based on the
results of un-instrumented load tests. This had led to designers using similar design parameters for
both CFA and displacement piles. To address the concerns of industry a series of instrumented piles
tests were performed by two Irish Universities. These tests summarized herein, revealed that CFA piles
develop higher shaft resistance than piles driven in glacial till. However, they exhibit low base stiffness
and the end bearing resistance that can be mobilized at acceptable pile settlement is low. The use of
simple non-linear elastic design approaches to predict the load-displacement response is considered.
The methods are used to predict the capacity of two large diameter CFA piles installed in glacial till.
While the predictions were reasonably accurate at predicting the initial load-displacement of the piles,
significant creep settlement developed at higher load levels. The cause of the creep settlement was
investigated through the use of plate load tests and the consequences for pile design are discussed.